Abstract:

An electric heating device for a motor vehicle includes at least one PTC
heating element with contact metal sheets extending substantially
parallel to one another and accommodating between them at least one PTC
element, and a printed circuit board. The printed circuit board has
formed therein at least one opening through which a contact tongue
projects. The contact tongue serves to establish an electric connection
between the PTC heating element and the printed circuit board. For
providing an electric heating device having a compact structural design,
a punched-out connection piece connected to a conductor path of the
printed circuit board in an electrically conductive manner. The
connection piece defines a fixing portion which rests on the printed
circuit board, and also defines and at least one spring tongue projecting
into the opening.

Claims:

1. An electric heating device for a motor vehicle, comprising:at least one
PTC heating element with contact metal sheets extending substantially
parallel to one another and accommodating between them at least one PTC
element, and a printed circuit board having formed therein at least one
opening through which a contact tongue projects, the contact tongue being
defined by a contact metal sheet and serving to establish an electric
connection between the PTC heating element and the printed circuit board,
wherein:a punched-out connection piece is connected to a conductor path
of the printed circuit board in an electrically conductive manner, said
connection piece defining 1) a fixing portion which rests on the printed
circuit board, and 2) at least one spring tongue projecting into the
opening.

2. An electric heating device according to claim 1, wherein the spring
tongue is located substantially within the printed circuit board.

3. An electric heating device according to claim 1, wherein the free end
of the spring tongue rests on a wall surrounding the opening.

4. An electric heating device according to claim 1, wherein a surface of
the spring tongue cooperating with the contact tongue is convex in shape.

5. An electric heating device according to claim 4, wherein a plurality of
spring tongues project into the opening from opposite sides.

6. An electric heating device according to claim 4, wherein the spring
tongues are arranged on opposite sides of the opening such that they are
displaced relative to one another.

7. An electric heating device according to claim 1, wherein the fixing
portion is arranged on the printed circuit board side facing the at least
one PTC element.

8. An electric heating device according to claim 1, wherein at least one
holding lug projects from the fixing portion, said holding lug being
produced by punching and bending and engaging a fastening hole formed in
the printed circuit board.

9. An electric heating device according to claim 8, wherein the fastening
hole is filled with a solder, and that the holding lug is electrically
connected to a conductor path of the printed circuit board.

10. An electric heating device according to claim 8, wherein the holding
lug and an intermediate piece located between said holding lug and the
fixing portion are cut out, by punching, in the form of a strip from the
metal sheet defining the fixing portion, and wherein the intermediate
piece is formed into a curved protruding shape by bending the strip
relative to a contact surface for the fixing portion, said contact
surface being defined by the printed circuit board.

11. An electric heating device according to claim 1, wherein the fixing
portion rests on a conductor path, which is formed on the surface of the
printed circuit board, in planar contact therewith.

12. An electric heating device for a motor vehicle, comprising:at least
one PTC heating element with contact metal sheets extending substantially
parallel to one another and accommodating between them at least one PTC
element, and a printed circuit board having formed therein at least one
opening through which a contact tongue projects, the contact tongue being
defined by a contact metal sheet and which serves to establish an
electric connection between the PTC heating element and the printed
circuit board, whereinat least one punched-out connection piece is
connected to a conductor path of the printed circuit board in an
electrically conductive manner, said connection piece defining 1) a
fixing portion which rests on the printed circuit board, and 2) a
plurality of spring tongues projecting into the opening from opposite
sides and being arranged on said opposite sides of the opening such that
they are displaced relative to one another.

13. An electric heating device according to claim 12, wherein the free end
of the spring tongue rests on a wall surrounding the opening.

Description:

BACKGROUND OF THE INVENTION

[0001]1. Field of the Invention

[0002]The present invention relates to an electric heating device for a
motor vehicle, comprising at least one PTC heating element with contact
metal sheets extending substantially parallel to one another and
accommodating between them at least one PTC element, and a printed
circuit board having formed therein at least one opening through which a
contact tongue projects, which is defined by a contact metal sheet and
which serves to establish an electric connection between the PTC heating
element and the printed circuit board.

[0003]2. Description of the Related Art

[0004]Such electric heating devices, which are also referred to as PTC
heating devices, are used in motor vehicles for the purpose of heating.
EP 1 157 867, for example, discloses an electric heating device in which
a plurality of heat-generating elements are accommodated in a frame, said
heat-generating elements being defined by two contact metal sheets
extending parallel to one another and by PTC elements successively
arranged between said contact metal sheets in one plane. These
heat-generating elements are provided in alternating sequence with
heat-emitting elements. The thus defined layered structure is held in a
pretensioned manner in a frame.

[0005]Selected ones of these contact metal sheets of the individual
heat-generating elements are laterally extended beyond the heating block
so as to provide contact tongues for electrically connecting thereto the
heating block. In EP 1 157 867 these contact tongues extend through
openings in a printed circuit board populated with components. On the
side facing away from the heating block, the printed circuit board
carries a spring element which projects beyond the printed circuit board,
said spring element clamping the contact lug and effecting electric
contacting with the printed circuit board.

[0006]A similar structural design with respect to contacting between the
contact tongue and the printed circuit board is known from EP 1 872 986.
In the case of this prior art, two respective contact metal sheets
accommodate between them a plurality of PTC elements that are stacked one
on top of the other. The resultant heat-generating element is
pretensioned by a wedge element acting from outside, said wedge element
resting on a pocket and being forced into said pocket, so that the
individual layers abut on one another in good contact with one another.
Hence, the wedge element has the function of a spring by means of which
the layered structure is held in a pretensioned manner within the frame
in the case of EP 1 157 867 A1. Also in EP 1 872 986 the contact tongues
defined by the contact metal sheets extend through openings in the
printed circuit board so as to be clamped in position in spring elements
projecting beyond the printed circuit board on the back facing away from
the heat-generating elements.

SUMMARY OF THE INVENTION

[0007]The present invention is based on the problem of providing an
electric heating device having a compact structural design.

[0008]For solving this problem, the present invention provides an electric
heating device having at least one PTC heating element with contact metal
sheets extending substantially parallel to one another and accommodating
between them at least one PTC element, and a printed circuit board having
formed therein at least one opening through which a contact tongue
projects. The central tongue is defined by a contact metal sheet which
also serves to establish an electric connection between the PTC heating
element and the printed circuit board. A punched-out connection piece is
connected to a conductor path of the printed circuit board in an
electrically conductive manner. The connection piece defines 1) a fixing
portion which rests on the printed circuit board, and 2) at least one
spring tongue projecting into the opening.

[0009]The printed circuit board can be any printed circuit board,
irrespectively of whether it is populated with components, or whether it
only comprises conductor paths for conducting current between two points.
Such a conductor path can be provided e.g. for the purpose of providing
electric connections on the electric heating device at a location remote
from the contact metal sheets. Normally, the contact metal sheets are
extended such that they extend straight beyond the heating block and
through the opening in the printed circuit board. When processed by
punching, contact metal sheets can also provide a plug contact which is
oriented, in an arbitrary direction, at an angle relative to the
longitudinal direction of the contact metal sheets of the heating block,
but, for reasons of manufacturing technology, such embodiments are
considered to be limited with respect to their three-dimensional size. In
this connection it is also of interest that the installation space
available for accommodating the electric heating device in the motor
vehicle is normally limited.

[0010]This is where the present invention comes into play. The present
invention suggests that, for electrically connecting the contact tongue
extending through the printed circuit board, at least one spring tongue
projecting into the opening should be formed. This spring tongue
constitutes part of a connection piece comprising, in addition to said
spring tongue, at least one fixing portion which is normally in full-area
contact with the printed circuit board. This fixing portion serves, on
the one hand, to fix the connection piece to the printed circuit board.
On the other hand, said fixing portion is normally used for establishing
an electric connection between the spring tongue and, consequently, the
contact metal sheet and at least one conductor path of the printed
circuit board.

[0011]Other than in the case of the prior art in which the spring element
used for the purpose of holding and establishing an electric contact with
the printed circuit board projects beyond the printed circuit board to a
substantial extent--a circumstance in view of which the printed circuit
board and the components mounted thereon have considerable dimensions in
the longitudinal direction of the contact metal sheets--the spring tongue
clamping the contact metal sheet is located in the opening formed in the
printed circuit board for passing the contact tongue therethrough.

[0012]According to a preferred embodiment which does not lead to any
substantial increase in the dimensions of the printed circuit board in
the direction in which the contact metal sheets extend, the spring tongue
is located essentially in the plane defined by the printed circuit board.
Preferably, the spring tongue is located fully within the plane of the
printed circuit board in accordance with this preferred embodiment, i.e.
the free end of the spring tongue, which is normally provided on the
printed circuit board side facing away from the fixing portion, does not
project beyond the printed circuit board.

[0013]Preferably, the spring tongue branches directly off from the fixing
portion on the level of the opening and extends from the fixing portion
exclusively in the direction of the opening. A spring tongue having this
type of structural design does not, or only to an insignificant extent
increase the thickness of the printed circuit board. Hence, the electric
connection to the contact metal sheet can be established in an extremely
space-saving manner.

[0014]For establishing a contact which is as solid as possible between the
spring tongue and the contact tongue, a further preferred embodiment of
the present invention suggests that the free end of the spring tongue
should rest on a printed circuit board wall surrounding the opening. This
wall extends normally at right angles to the upper and lower surface of
the printed circuit board. A spring tongue supported in this way will be
able to apply a comparatively high clamping force to the contact tongue,
whereby a better contact between the contact tongue and the spring tongue
will be established.

[0015]With respect to a defined contact area between the spring tongue and
the contact tongue, a further preferred embodiment of the present
invention suggests that the spring tongue surface cooperating with the
contact tongue after insertion of said contact tongue should be convex in
shape. This convex configuration can preferably be provided by shaping
the surface of the spring tongue. The convex shape leads to a
point-shaped or linear contact between the spring tongue and the contact
tongue which normally consists of a flat sheet metal strip. Accordingly,
the spring force generated by the spring tongue is transmitted to the
contact tongue via a small but defined contact area, and this results in
safe and reliable contacting.

[0016]According to another preferred embodiment of the present invention,
respective spring tongues are formed on opposite sides of the opening.
All these spring tongues project into the opening and are preferably
connected to a common fixing portion which rests on the surface of the
conductor path. The spring tongues are preferably formed such that they
are displaced relative to one another and they are provided in an
alternating mode of arrangement by cutting them out and bending them away
from the sheet metal plane of the semi-finished product so that the
respective spring tongues are arranged in front of opposed walls of the
opening and clamp the contact tongue between them.

[0017]According to a preferred embodiment, the fixing portion rests on the
printed circuit board side facing the at least one PTC element, so that,
when the contact tongue is being inserted with application of an elastic
bias force of the spring tongue, the resultant frictional force will be
maintained across the contact area between the fixing portion and the
surface of the printed circuit board. Especially, there is no risk that
the connection piece, in particular the fixing portion, will be raised
from the printed circuit board when the contact tongue is being inserted
into the opening.

[0018]According to another preferred embodiment of the present invention,
the connection piece is provided with at least one holding lug, which is
produced by punching and bending the sheet metal strip defining the
connection piece. This holding lug projects from the connection piece,
normally approximately at right angles thereto, and is in engagement with
a fastening hole formed in the printed circuit board. This holding lug
allows, on the one hand, an exact positioning of the connection piece
during mounting. The connection piece is only mounted at the exact
position relative to the printed circuit board, when the at least one
holding lug has been brought into engagement with the associated
fastening hole.

[0019]According to a preferred embodiment, the fastening hole is
additionally filled with a solder, and the holding lug is electrically
connected to a conductor path of the printed circuit board. The solder is
normally in contact with the circumferential surface of the fastening
hole, which, in turn, is lined with an electrically conductive coating.
The fastening hole should be provided with a copper coating on its
circumferential surface, preferably on the inner side thereof, said
copper coating providing a good electric connection between the holding
lug, the solder accommodated in the fastening hole and a conductor path
which is formed on the upper and/or lower surface(s) of the printed
circuit board and which is electrically connected to the circumferential
coating of the fastening hole.

[0020]The holding lug has preferably a width that corresponds
approximately to the diameter of the fastening hole. A precise
positioning of the connection piece after insertion of the holding lug in
the fastening hole is accomplished in this way.

[0021]Preferably, the holding lug and an intermediate piece located
between the holding lug and the fixing portion are cut out, by punching,
in the form of a strip from the metal sheet defining the fixing portion,
and that the intermediate piece is formed into a curved protruding shape
by bending the strip relative to a contact surface for the fixing
portion, said contact surface being defined by the printed circuit board.
This development supports this precise positioning of the holding lug in
the fastening hole. According to this further development, an
intermediate piece, which is implemented such that it is curved relative
to the printed circuit board, is provided between the holding lug and the
fixing portion that rests on the printed circuit board. The holding lug
and the intermediate piece are preferably cut out in the form of a strip
by punching the sheet metal defining the fixing portion. The intermediate
piece is formed into a curved protruding shape by bending the strip
relative to the printed circuit board contact surface provided for the
fixing portion. Hence, the strip part projecting from the lower surface
of the fixing portion extends preferably at an angle of precisely
90° C. to this lower surface, whereby precise insertion and
positioning will be guaranteed while maintaining a planar contact between
the fixing portion and the upper surface of the printed circuit board.

[0022]The fixing portion is preferably in planar contact with,
particularly preferred in full-area contact with a conductor path formed
on the surface of the printed circuit board.

[0023]Further details and advantages of the present invention can be seen
from the following description of an embodiment in combination with the
drawing, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1 shows a perspective view of an embodiment of a PCT heating
element connection piece;

[0025]FIG. 2 shows the embodiment according to FIG. 1 in a perspective top
view after mounting of the printed circuit board of the PTC heating
element;

[0026]FIG. 3 shows a sectional view along line according to the
representation in FIG. 2;

[0027]FIG. 4 shows a sectional view along line IV-IV according to the
representation in FIG. 2; and

[0028]FIG. 5 shows a sectional view along line V-V according to the
representation in FIG. 2 with a contact tongue projecting through the
printed circuit board.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029]FIGS. 1 and 2 show perspective views of an embodiment of a
connection piece per se (FIG. 1) and after incorporation in a printed
circuit board, which is identified by reference numeral 1 and which has
provided thereon a conductor path 2 on the upper surface thereof, said
conductor path 2 consisting of copper. A connection piece 3 rests on the
conductor path 2. The essential components of said connection piece 3
will be explained hereinbelow with reference to FIGS. 1 and 2.

[0030]The connection piece 3 is provided with a fixing portion 4 defined
by a flat sheet metal strip. In the middle of this fixing portion 4,
spring tongues 6 are provided in an alternating mode of arrangement on
opposite sides of an elongate opening 5. The spring tongues 6 are formed,
by punching and bending, from the sheet metal strip defining the
connection piece 3. The spring tongues 6 are all bent towards the lower
surface or contact surface of the connection piece 3, which is shown in
FIG. 1. Each spring tongue 6 has a contact area 7 bulging convexly so as
to form the convex area of the curvature of the spring tongues 6. This
contact area 7 projects beyond the curved outer surface of the spring
tongue 6 provided in the longitudinal direction of the spring tongue 6.
The connection piece 3 has provided thereon holding lugs 8, which are
arranged at opposite ends of the connection piece 3 and diagonally
relative to one another. Also these holding lugs are produced by punching
and bending. In so doing, a strip extending in the longitudinal direction
of the sheet metal strip is first cut free from the sheet metal strip
defining the connection piece 3. Between the fixing portion 4 and the
holding lug 8, this strip is formed into an intermediate piece 9 by
bending, said intermediate piece 9 projecting beyond the fixing portion 4
on the outer side thereof in a curved configuration and interconnecting
the holding lug 8 and the fixing portion.

[0031]As can be seen from the above description, the connection piece 3 is
formed exclusively by subjecting a sheet metal strip to punching. The
fixing portion 4 defines an area of contact resting on the printed
circuit board 1 and, consequently, a flat area allowing accurate
positioning and contacting with the printed circuit board. The holding
lugs 8 serve to position and fix the connection piece 3 in the printed
circuit board and to establish an electric contact between said
connection piece and said printed circuit board, in manner that will be
described hereinbelow.

[0032]The spring tongues 6 of the preferred embodiment of the connection
piece and, consequently, also all the elements of said connection piece
are preferably made of copper beryllium (BeCu25). For reasons of costs,
preferably only the contact areas 7 of the spring are provided with a
silver coating having a thickness of 2.5 μm.

[0033]FIG. 2 shows the connection piece 3 when it has been arranged on the
printed circuit board. The spring tongues 6 are now positioned in an
opening 10 (cf. FIG. 5) formed in the printed circuit board and used for
receiving therein a contact tongue extending through said opening and
defined by a contact metal sheet which is not shown.

[0034]In FIG. 2 areas for SMD handling are additionally provided, said
areas being identified by rings 11. Via these areas, the connection piece
3 is held and positioned on the printed circuit board during mounting.

[0035]As can be seen from FIGS. 2 to 4, the conductor path 2 defines the
contact surface for the connection piece 3. The lower surface of the
fixing portion 4 is in full area contact with the conductor path 2. The
holding lug 8 extends through a fastening hole 12, which is formed in the
printed circuit board 1 and which is coated with the material of the
conductor paths (copper) on the inner circumferential surface thereof.
The holding lug 8 is inserted into this fastening hole 12 and fixed in
position therein by means of a solder. A solid electric contact with the
conductor path 2 is established in this way and, in addition, the
connection piece 3 is thus fixed to the printed circuit board 1. As can
especially be seen in FIG. 4, the width of the holding lug 8 corresponds
approximately to the diameter of the fastening hole 12, so that, when the
holding lug 8 is introduced in the fastening hole 12, the connection
piece 3 is fixed very accurately relative to the printed circuit board 1.

[0036]FIG. 5 shows a sectional view along line V-V according to the
representation in FIG. 2 and, consequently, a cross-sectional view
through the elongate opening 5 of the printed circuit board 1. It must be
imagined that the heat-generating PTC element or elements are arranged
such that their respective contact metal sheets are arranged below the
printed circuit board 1 with respect to the representation according to
FIG. 4. The part of this heat-generating element shown in FIG. 5 is only
the end of a contact metal sheet 13, which is implemented as a contact
tongue 14. This contact tongue 14 is passed through the opening 10 of the
printed circuit board 1, i.e. it projects through the printed circuit
board 1. The contact tongue 14 passes through said opening between
opposed spring tongues 6, which, due to the contact tongue passing
therethrough, are displaced towards the walls 15 delimiting said opening
10. This displacement is caused by resilient bending of the spring
tongues 6 at the point where they branch off from the fixing portion 4.
The contact tongue 14 only acts on the contact areas 7 of the respective
spring tongues 6. When the contact tongue 14 is being inserted between
the spring tongues 6, the free ends of these spring tongues 6 are finally
brought into contact with the inner wall 15 of the opening 5; this
results in an increased spring force, which has the effect that the
contact tongue 14 is reliably contacted and press-fitted between the
spring tongues 6. Since the insertion of the contact tongue 14 takes
place from the printed circuit board side on which the fixing portion 4
of the connection piece 3 abuts, said connection piece 3 is pressed
against the lower surface of the printed circuit board 1, when the spring
tongues 6 resist the insertion movement of the contact tongue 14 to a
certain extent. This kind of contact with the lower surface of the
printed circuit board 1 provides a reliable countersupport for the
connection piece 3 at any time.

[0037]As can be seen in FIG. 5, the spring tongues 6 in their entirety are
located within the opening 10, i.e. between the upper and the lower
surface of the printed circuit board 1. A very compact structural design
is provided through which an electric connection between the contact
tongue 14 and the conductor path 2 of the printed circuit board 1 can
easily be established. The spring tongues 6 are shaped such that e.g. a
contact tongue having the shape of the contact tongue 14 shown in FIG. 4
can also be inserted into the opening 10 from the opposite side and
contacted with the printed circuit board 1. All the connection pieces 3
should preferably be mounted on the printed circuit board 1 from the same
side. This printed circuit board side, which will be referred to as
mounting side in the following, may also be the side carrying exclusively
the components fixed to the printed circuit board 1. On the basis of this
structural design, the final assembly of the printed circuit board 1 can
be executed from one side, i.e. exclusively from the mounting side.